Please learn me on disc rotors

[Clancy]

Can people chime in on brake pads while this discussion is going on?

Do certain brand brake pads work better with specific brand rotors? Are any after market companies the go to?

I have a GRX group on one bike with Ultegra level rotors, CL. The front brake squeals like a scalded cat on meth and I’ve done everything I’ve been taught - cleaned rotor and pads with alcohol ( many times) sanded down pads ( 2-3X) carefully bedded in the pads ( after every cleaning and sanding ) checked torque on caliper mounting bolts, to no avail. I have a set of SRAM Red brakes on another bike, whisper quiet.

Absolutely puzzled

[Hilltopperny]

Originally Posted by Clancy

Can people chime in on brake pads while this discussion is going on?

Do certain brand brake pads work better with specific brand rotors? Are any after market companies the go to?

I have a GRX group on one bike with Ultegra level rotors, CL. The front brake squeals like a scalded cat on meth and I’ve done everything I’ve been taught - cleaned rotor and pads with alcohol ( many times) sanded down pads ( 2-3X) carefully bedded in the pads ( after every cleaning and sanding ) checked torque on caliper mounting bolts, to no avail. I have a set of SRAM Red brakes on another bike, whisper quiet.

Absolutely puzzled

Tough to say. I have used all three of the major brands disc brakes at this stage and my Sram Force hydros have been the noisiest IME. My Shimano brakes would squeal when wet when some grime got in, but not as frequently.

My Campagnolo have been the best so far. They are made by Magura and I am using them with Jagwire Pro rotors. So far these have been the most silent and best modulating road discs I have used.


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[Johnnyg]

put the pads on a non flammable surface, burn them with a torch, sand clean with alcohol, good to go. good luck

[joevers]

Originally Posted by Clancy

I have a GRX group on one bike with Ultegra level rotors, CL. The front brake squeals like a scalded cat on meth and I’ve done everything I’ve been taught - cleaned rotor and pads with alcohol ( many times) sanded down pads ( 2-3X) carefully bedded in the pads ( after every cleaning and sanding ) checked torque on caliper mounting bolts, to no avail.

Pads are not always salvageable if they've got oil on them at some point (lube, mineral oil, from your hands etc). It sounds like you've done everything shy of that, so I'd really thoroughly clean the rotor with soap and water and then alcohol and replace the pads. Soapy water is fine on rotors and alcohol is so you can get all the residue off and because it evaporates really quickly leaving nothing behind.

Those brakes and rotors should be pretty silent. I'm not sure what pads are being stocked with GRX but resin pads are going to be quieter and Shimano usually gives you a few options. As long as the first letter is the same as the pads already in your brake you can get any others from Shimano. SwissStop aftermarket pads (if they make them in that shape) are extremely quiet also.

[guru]

On a road bike do the XTR rotors seem to be more durable from warping and scoring than do the Dura Ace rotors ?

[Applesauce]

Originally Posted by joevers

Those brakes and rotors should be pretty silent.

If Shimano brakes are working properly, they should be silent, yes. But they have a few latent issues, all of which generate untold noise and ineffectual braking in way too many cases. First, they’re super sensitive to break-in. I don’t know if it’s the pad compound or in combination with the rotors (it’s not the rotors alone, because I’ve used them for years with SRAM and Magura brakes without similar issues), but if they’re not broken in perfectly, the pads are often ruined: there’s no second chance at “re-breaking” them in.

Second, and I believe related, is the fact that many Shimano brakes (both with plastic and ceramic pistons) leak at the square seal over long periods of disuse. The pads are naturally osmotic and take on this mineral oil, which ruins them. (I’ve seen the rotors ruined from glazing in such cases too, but that requires great commitment and is rare.) Shimano hasn’t admitted to this - they lead the pack in “oh, we’ve never heard of that!” warranties - but there’s a lot of folks like myself with experiential evidence that points to this alone.

That said, along with their mea non culpa response, they usually just replace the pads in such cases. For $50 pads, this is significant. And a reason it pays to have a healthy relationship with your LBS: if I have any suspicions, I replace the pads from my stock and let Shimano make me whole.

Magura/Campagnolo have the fewest noise issues, in my experience, but SRAM is a close second with an undeserved reputation for such issues (if anything, they’re usually just overfilled when new).

And of course, flat mount sucks: the axis of adjustment is on a different plane than the rotor itself, resulting in great difficulty in getting caliper pistons actually parallel to the rotor face.

[benb]

It hasn't been said yet but whatever you choose follow the manufacturer recommendations..

Don't mix and match cause you think you know better than Campy/SRAM/Shimano/Whatever...

If they say use the following rotors with the following pads with the following system then that's going to be the best option.

So much of the FUD on road disc came about due to journalists/influencers mixing and matching against manufacturer instructions/warnings to save grams. Hopefully we're getting past that.

[Applesauce]

Originally Posted by guru

On a road bike do the XTR rotors seem to be more durable from warping and scoring than do the Dura Ace rotors ?

No.

[thwart]

Originally Posted by Johnnyg

put the pads on a non flammable surface, burn them with a torch, sand clean with alcohol, good to go. good luck

Should be noted by anyone on the fence about buying a disc bike.

From someone in that situation, this thread has been yet another reason to rethink things... 'let's see... I seldom ride in the rain... there are no really long, steep descents around here... I can run wide tires on my rim brake bike... OK, why do I need the hassle of a disc bike right now?'

[Jaybee]

Originally Posted by guru

On a road bike do the XTR rotors seem to be more durable from warping and scoring than do the Dura Ace rotors ?

Originally Posted by Applesauce

No.

This has been my experience as well. Shimano rotors seem to warp a bit after really hard use, then shift back into shape as they cool. The issue seems to be worse the lighter the rotor is.

For this reason, all my bikes with Shimano brakes are running XT or SLX level rotors.

My only all the time quiet brakes are SRAM Guide RSCs.

[davidb]

To the above and the howling brakes. Has the frame/fork been faced? I have had great success using the VAR tool. Park tools works but is not "easy". It is an uncomfortable reality that shops selling flat-mount disc brake bicycles will need to face forks/frames.

[elladaddy]

I've been speculating that Shimano brakes need additional cooling over sram, because mineral oil doesn't handle heat as well as DOT.

I've seen shimano brake oil come out black. That seems a bit disturbing. So I like that Shimano rotors have so much cooling built in.

I'll bet it's the abundance of softer aluminum and the thinner arms of their road rotors that briefly warps under hard braking. It probably even indicates the cooling is working.